One of the most prominent trends in the wind construction sector is moving toward low-cost providers without giving up experience. Also, with the experience many companies now have, each is developing its own approach to constructing quality farms faster. It’s no surprise that specialized software assists with this task. Lastly, the greatest challenge facing the construction sector will be learning to build offshore.

Dave Hart, wind energy manager at Michels Corp., says last year his company saw the first low-cost providers winning bids. However, he explains low-cost bids can often mean higher risks, because providers don’t have adequate experience. “Some companies make it seem like they’re reducing costs through construction management, but in reality these lower costs mean higher risk. This is because the scope-of-work changes from their bid to actual execution against schedule and specification.” In other words, many companies were winning projects because of their low bids, but failed to execute the work they promised. Many low-bid companies lack experience, which could lead to longer and more expensive projects. Developers this year realize they need to find a medium between quality and cost.

The good news is that now many companies are experienced in wind-farm construction. For instance, Mortensen Construction just finished its 100th project, after 16 years in the industry. Jerry Grundtner, VP of project development, says this experience has lead companies to form their own approaches to building. “We take a continuous improvement approach, focusing on efficiency and increased productivity to reduce cost and construction time,” he says. On the other hand, Hart says his company focuses on executing all work internally against schedule and specification to minimize risk, cost increases, and schedule lag.

Another trend involves designing wind farms to satisfy a variety of constraints. “The ultimate goal is to maximize energy capture while minimizing wind loads on turbines and balance-of-plant costs. Yet, we must maintain all setback and avoidance criteria,” says Jay Haley with EAPC Wind. He says this is accomplished with wind software options such as WindPro. Another area where wind-farm designing has gone high-tech is in fluid-flow simulations and lab experiments. Researchers at Johns Hopkins and Belgium’s Leuven University used these methods to study how turbine blades distort wind, creating eddies and turbulence that can affect other turbines farther downwind. This is especially problematic as turbines and farms in general, trend larger. As a result, researchers have developed a model to calculate best turbine spacing.

Finally, as the U.S. continues with offshore development, construction methods will have to adapt. Joel Whitman, CEO of Global Marine Energy Inc., speaks from an offshore cable perspective. “Take a Cape Wind-sized project, for example,” he says. “Its total cost is about $2 billion with the cable install work about 7% of that. Double that figure for supplies as well. So about 15% of all costs are cable related,” he says. The offshore wind industry will have to face cabling issues, while having to use special vessels and work in a short weather window. But Whitman, sees these challenges as not insurmountable and says the industry is moving in the right direction.

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Paul Berberian, Alignment Supplies Inc., Maumee, Ohio

Of all the mechanical maintenance problems in wind turbines, shaft alignments are probably easiest to understand. The high-speed shaft between a gearbox and generator is a critical point of failure. Their misalignment a leading cause.

Precision-shaft alignments involve aligning the center line of the shafts of one or more rotating machines. When the shaft center lines are co-linear, the two turn freely mitigating external forces that could destroy key components of the system, such as bearings, seals, and couplings. Misalignment most affects the main bearings in the gearbox and generator. When left unattended for too long, it will destroy the bearings and then go to work on other components down the line on the shaft – seals, rotors, and so on.

A precision shaft alignment at install and periodic checks can help prevent component failures, up-tower repairs, and catastrophic failures. For instance, fixing a bearing up tower can cost $10,000 to $15,000. Catastrophic failures can cost up to $260,000. A good alignment program can stop these problems before they even start.

Alignments are done with several tools, some better than others. For instance:

Straight-edge mechanical tools

• Do not provide a precision alignment and are

• Subject to gross user interpretation

Dial indicators

• Must be mounted on the shafts

• Time consuming for the inexperienced

• Difficult to learn a proper alignment method

• Shafts must turn to align with dials

• Subject to user interpretations

Laser alignment tools have

• A short learning curve

• Precision, even from inexperienced users

• Many mounting options for different turbines

• Shafts need not turn

• No interpretation by the user. The data is
the data

Laser alignment equipment attaches to driver and driven shafts.

Precision alignment means using a laser alignment kit or dial indicators. (A straight edge is not a precision alignment tool.) Lasers have many advantages over dial indicators. For one, dials are hard to teach and learn. Until you have mastered the art of dial indicators, they can be frustrating and time consuming. Lasers, on the other hand, are a fast, easy, and accurate when used to align shafts.

Good laser-alignment tools have options for mounting in wind turbines. Different brands of turbines present different challenges. For instance, the position of the brake calipers and discs can prevent mounting with a chain and bracket on the shaft. When the shaft turns for alignment work, the measuring units (laser and detectors) must turn without obstruction. Hence, mounting options must take those clearances into consideration. Lastly, a proper alignment job is not complete without a good electronic method for documentation.

Condition monitoring can help detect alignment problems. Vibration-monitoring tools for example, look at the mechanical components such as bearings and gears, but they also helps identify the root cause of an existing problem and predict component failure. Condition monitoring can detect misalignment problems before they damage mechanical components. Angular misalignment, for instance shows in the vibration spectrum in the axial direction, typically showing high vibration at 1x or 2x turning speed. Offset misalignment more typically shows up in a radial measurement, when the vibration signal at 2x turning speed is greater than at 1x.

The increase in vibration at twice running speed in the spectrum shows a misalignment condition that is worsening and causing damage. Using vibration to detect a misalignment problem and a laser shaft-alignment tool for correction, prevents serious mechanical issues.

Consider several issues when aligning wind turbine shafts. Safety is first and foremost. Laser alignment tools must be mounted in such a way that they will not contact the techs if the turbine brakes give way. Turning the shafts is critical to performing a precision alignment. O&M teams working up-tower must be aware of conditions that result in turning the blades, and hence, the shafts. Taking a measurement without turning the shaft is becoming a more predominant requirement. Still, a sudden strong gust of wind can catch the maintenance team off guard and cause the shaft to spin freely as the brakes are released for the alignment.

Some turbine manufacturers have developed solutions for alignment work that do not require turning the gearbox. These solutions require special fixtures and removing the coupling to perform the alignment. However, it is the safest way to perform an alignment in a wind turbine. Know the guidelines that your turbine OEM has set for up-tower alignments, such as maximum wind speed and direction the turbine should face. Also ask: Can the shaft covers be off or on and should the coupling be removed? Make sure your maintenance teams are safety trained as well.

A second consideration is deciding how often to align the turbine. Many turbine OEM’s have set requirements for turbine alignment intervals. Some OEM’s only align prior to shipment from the manufacturing facility. Others align when the turbine arrives “in-country”, or during installation. Some do all three. It is never a bad idea to check turbine alignment. Include a precision alignment check during intervals of preventative maintenance. You can even check the alignment fairly quickly when it is not scheduled. Once you determine that an alignment is required, you can schedule it in your maintenance plan.

Another important consideration: Alignment tolerances. These define an acceptable misalignment for a given turbine model. Many turbine OEMs have established alignment tolerances for their equipment. If you don’t know the manufacturer’s tolerances, or they are not supplied, tolerance charts are available based on speed of rotation.

A last thing to consider for this article is dynamic movement. This happens when the brake is released and the hub and blades turn freely. Weight and turning forces can cause the gearbox to move slightly – even imperceptibly to the human eye – and cause misalignment. Consult your turbine manufacturer to find out if dynamic movement is present in their turbines, if they know how much it moves, and whether or not it is critical. In some cases, the coupling can offset the movement when the shafts are aligned within tolerance. Once you know the amount of movement, add those calculations to an alignment tool. Compensating for dynamic movement means actually misaligning the gearbox and generator at rest so that when they are running, the machines will move into alignment.

Lasers are also used in the wind industry to measure flanges on wind towers and blade-root flanges. Flatness and taper measurements help ensure that these components fit properly during construction.

Precision alignment is a vital first step in preventing mechanical failure in wind turbines. whether the OEM, an O&M contractor, or an O&M team performs the alignment, good tools and training are not optional. Remember, an ounce of prevention is worth a pound of cure, and prevention lessens the chance for catastrophic, up-tower, machine failure. WPE

Conventional turbines are perched 60 to 80-m off the ground where the wind is stronger. But what about the wind below those elevations? California-based Wind Harvest International says it has a solution in a straight-bladed, vertical-axis wind turbine that offers the first cost-effective solution to harvesting high energy, turbulent near-ground winds. “Using a methodical approach of designing, building, and verifying, we’ve constructed 11 different models,” says WHI CEO Kevin Wolf. “In that process, we discovered the coupled-vortex effect,” he adds.

WHI’s Wolf envisions building the model 3000 beneath conventional turbines on wind farms. The man at the third turbine provides scale.

“We had run one turbine by itself collecting data for a year and then placed others on either side of it, spacing them so blades were two to three feet apart,” says Wolf. “Surprisingly, the energy output from the center turbine increased. Adjacent turbines counter rotate, so the area between blades generates a convergence area with the wind speeding up there, letting the turbines capture more energy than if more widely separated.” Wolf’s turbine array are patented for the discovery.

He says they have discovered something with each model. For example, a mechanism on the lower portion can pitch to stall in high wind. And the external structure keeps damaging loads off the center bearings. As a result, WHI’s Linear Array Vortex Turbine Systems (LAVTS) can hit peak efficiencies near the theoretical limit for any type of wind turbine design and will be among the most cost effective of any design.

The largest market for LAVTS is expected to be wind farms with good near-ground wind resources, the “understory” or area beneath horizontal-axis wind turbines. This includes most wind farms in California and about one-fourth of others around the world.

There are other large markets for the company’s turbines, says Wolf. “One is the UK’s feed-in-tariff market, which is limited to turbines with less than 100kW in capacity. WHI’s models 636 and 1500 meet U.K. requirements and will be profitable at high-wind sites.

The lower blades on the WHI model 530G can pitch to stall in high wind.

Another is a “standalone” market, one in which buyers install WHI’s Linear Array Vortex Turbine Systems in locations where there are no tall horizontal axis wind turbines.

“Our time line is to install in Sept-ember and then go through four to six months of durability tests in Scotland,” says Wolf. He estimates that about one-fourth of existing wind farms around the world have 14 mph or better winds at 30 ft above ground. The estimate comes from large geographic areas with features such as passes, ridgelines, mountains, coastal bluffs, and mesas. For example, all major passes in California qualify with a capability of collectively doubling the existing 3,000 MWs with LAVTS. Wolf says many other countries also have promising terrain.
The non-wind-farm market is also growing, says Wolf. For example, the U.K. instituted a feed in tariff in April 2010 that will let people, businesses, and municipalities purchase wind turbines up to 100 kW and receive an equivalent of $0.15 to $0.50/kWh produced.  Installation is restricted to sites with less than 5 MW of capacity.
WPE

A study by the Lawrence Berkeley National Lab of 7,390 homes surrounded by some 1,300 turbines in several states found that wind farms do not depress land values.

Community-wind developers often encounter some opposition when developing projects. It may surface as misinformed, for example, insisting that the turbines kill birds and wind farms depress land values, among other things. They are not true but the charges deserve more detailed explanations to effectively dispel them. Hence, this column and others to follow will deal with such misinformation and with the goal of a better informed populace. Here’s installment one.

Issue 1: Wind turbine syndrome or WTS, disrupts the lives of some people who live near wind turbines. The expansion of wind farms, therefore, should proceed more slowly.

The facts: The syndrome reached national attention after Nina Pierpoint self-published a non-peer reviewed book on the topic. She reported a variety of symptoms that some say keep them awake at night with a low level thumping and headaches. Others report different symptoms. Her theory is that inaudible low frequencies or infrasound, 1 to 2 Hz, activates the vestibular system and vibrates the chest. Another possibility she theorizes, is that infrasound at 4 to 8 Hz enters the mouth and lungs and disturbs the diaphragm. A definitive cause, however, remains uncertain.

The wind industry wants to address the issue at a serious level, so it hired experts to investigate the allegations and the syndrome. But before that, the industry tried engaging public-health authorities. Their disappointing response was that the affected group was too small and funds insufficient to cover the costs of an investigation. So, the industry funded a study to learn more.

Experts such as Geoff Leventhall and W. David Colby, both medical researchers have separately delved into the subject. Leventhall found the initial research flawed and unsupported by other researchers. He says WTS seems based on uncontrolled and unverified reports of nonspecific symptoms in 38 people interviewed by Pierpont. They apparently had no physical exams or diagnostic testing which might have found other causes for the symptoms. Subjects were selected for the investigation, says Leventhall, using criteria that expose extreme selection bias, leaving Pierpont’s conclusions suspect. Interested readers can hear their comments in a webinar at http://tinyurl.com/wpe-myths.

Leventhall does not dismiss WTS but concludes: “It appears there is no specific WTS but there are stress effects from low-noise levels, either high or low-frequency noise, which affects a small number of people. The audible swoosh-swoosh which, when it occurs, is the cause, not infrasound or low-frequency noise.”

Issue 2: Wind farms decrease land values.

The facts: Not true. An exhaustive scientific study done by the Lawrence Berkeley National Laboratory examined land values over time and found no supporting evidence. The study by Ben Hoen and colleagues at the national lab, examined 7,390 homes surrounded by some 1,300 turbines in several states. Their report, available at http://tinyurl.com/landvalues, concludes that although, “One cannot rule out isolated cases where property values are negatively impacted, any such impacts within our sample are neither widespread nor statistically identifiable.”

Issue 3: Wind turbines kill birds.

The facts: Definitive bird studies or avian issues have cost millions of dollars, and organizations continue to spend on them. The studies often find that wind turbines have only an incidental effect on some birds. It is usually not a concern for populations for a region. In a few instances, projects did not have as much siting control before being built, and so there are a few issues. California’s Altamont pass is one. Tall buildings and cats kill more birds. Still, the issue is taken seriously and tracked, studied, and mitigated, at high cost. (Bats will be addressed in a separate column.)

Interested readers might look to the National Wind Coordinating Collaborative (nationalwind.org) for its many publications regarding wind wildlife studies. Even the Audubon Society and Sierra Club have recognized the studies as valid, accept their conclusions, and acknowledge that the wind industry treats the issue seriously.

So far, bird kills have caused serious scientific concern only in the Altamont Pass, one of the first areas in the country to experience significant wind development. Over the past decade, the wind community has learned that wind farms and wildlife can and do successfully coexist. The wind industry’s overall impact on birds is extremely low (<1 of 30,000) compared to other human-related causes, such as traffic and house cats. Birds can fly into wind turbines, as they do with other tall structures. However, some also insist that conventional fuels contribute to air and water pollution that can have greater impact on wildlife and their habitat. WPE